Dry-cell depolarizer



Aug. 23 1927. 1,639,985 B. K. BROWN DRY CELL DEPOLARI ZER Original FiledJuly 7, 1925 Q Q l/- R g 3 NV; a? -s 5 E g .S [/3 Q 2 .g

g E g *He "c [E S g 3 K? I 5/ Q Q w N V A 2 2 2 a 2/ 4 WW4) P INVENTORBRUCE KBFO WA/ ATTORNEYS Patented Augi23, 1927.

UNITED STATE PATENT-OFFICE.

BRUCE K. BROWN, 01' T33R13. HAU'I'E, ASSIGN'OB '10 0. 1'. 3mm mom-TORIES, INC., 0] MADISON, WISCONSIN, A. CORPORATION 01' DELAWARE.

DRY-cur. nnromrzim.

Original application filed July 7, 1985, Serial llo. v 1886. Serial Thepresent invention relates to galvanic cells and more particularly to drycells of the LeClanche type, wherein a solid depolarizing material ispresent at one electrode to oxidize the hydrogen there set free.

Dry cells of the LeClanche type as now constructed contain manganesedioxide in one or more of its forms or combinations as the depolarizingmaterial. In a copending application, Serial No.'42,090, filed July 7,1925, I have claimed a new galvanic cell using an oxide of carbon, suchas graphitic oxide, as the depolarizing medium. In the present inventionI substitute an oxide of carbon, such as graphitic oxide, which hasdepolarizing properties, for a portion of the manganese dioxide usuallyused in dry batteries.

The details of my invention will become clearer from the followingdescription taken in conjunction with the drawings herein: Fig. l is arectangular elevation of a dry cell, and Fig. 2 shows discharge curvesfor dry cells when operating under conditions hereinafter set forth indetail.

In the drawing the dry cell comprises a seamless zinc cup (1), whichserves as a container for the other elements of the cell. At the centerof the cup is a carbon rod provided with a brass cap (3), and held 1nplace by a seal (4) of pitch or sealing wax, poured in while hot andsupported on a paper washer (5). Associated with the carbon rod to formtherewith the cathode of the cell is a tightly compacted or molded block(6) of depolarizing mixture. This may be enclosed in a cheese clothenvelope (7), wrapped around with a thread (8). A gelatinizedelectrolyte (9) separates the cathode from the anode, as will beunderstood by those skilled in the art.

When manganese dioxide is used for depolarizing a dry cell, thedischarge curve has certain characteristics as illustrated in curve (A)of Fig. 2, where voltages have been plotted against time in minutes forcontinuous discharge of a typical cell through a four ohm resistance,the cell being of a size 7 in diameter and 1% tall.

When oxidized carbon is used as the depolarizer the discharge curve hassomewhat different characteristics as shown by curve (B) of Fig. 2,being characterized by lower 4:,092. Divided and um application fled n1;1,

open and closed circuit voltages, a quick drop in voltage to about .65volt on discharge, and a pronounced flattem'n of the discharge curve atthis voltage. y combining the two depolarizers in various proportions itis possible to modify the discharge curve to suit the requirements.

The oxide of carbon may be made by chemical or by electrochemicaloxidation and may be ground in a ball mill or may be left unground andcan well be of a fineness of 20 mesh.

A typical' flashlight mix follows, all parts being by weight: 15 partsoxide of carbon containing 7.85% available Oxygen, 15 parts manganesedioxide in the form of pyrolusite, 12 parts of pulverized graphite,which may be of the impalpable fineness described in U. S. Patent No.1,162,449, 4: parts of sal ammoniac, and a wetting solution. The abovemix will have a considerably higher electrical resistance than a mix ofthe same proportions but of which the 15'parts of oxide of carbon hasbeen ground in a ball mill to crack open the oxidized particles. It isalso possible to substitute for the 15 parts of oxide of carbon and 12parts of pulverized graphite specified in the above formula an oxide ofcarbon with lower oxygen content and which has been ground to a finestate of subdivision. It is also possible to use an equal amount ofartificial manganese dioxide in place of the pyrolusite.

I have further discovered that a highly eflicient depolarizing mixturemay be made by precipitating an artificial manganese dioxide onto theoxidized carbon particles. I believe that the increased efliciencyresulting from this method is due to the actual precipitation of themanganese dioxide in the oxide of carbon, the oxide being colloidal andtherefore able to absorb the solutions used for preparing the manganesedioxide. The manganese dioxide maybe precipitated by any of the knownmethods for preparing artificial manganese dioxide. Following is aspecification of a typical run which I have found to give excellentresults; 1,500 grams of graphite oxidized to contain 4.22 per cent offixed oxygen (ground or unground) are suspended in the followingsolution;

and

450 grams potassium permanganate; 16 liteis water; 50 c. c. nitnc acidconc 425 grams manganese sulphate dissolved in one liter of water. Thismixture is agltated occasionally for a 24 hour period after which it iswashed, filtered and dried. The yield should be over 1,900 grams ofsolid.

The above mixture may be used in the following proportions for making adepolarizing nnxture for dry cells:

parts manganese-treated ox1de of carbon; 12 parts impalpable aphite'; 4parts sal ammoniac; themass being wetted to the usual consistency.

Cores or cathodes are tamped in the usual manner as by aid of a tampingmachine, such as -is shown in U. S. Letters Patent No. 1,232,297, issuedJuly 3, 1917. The cores are then assembled in a zinc can using agelatinizable electrolyte to se arate the molded electrode from thezinc. uitable electrolytes are disclosed in U. S. Letters Patents No.

1,292,764, issued January 28, 1919, and No.

1,370,056, issued March 1 1921. The molded electrode may be providedwith a cheese cloth or other bibulous envelope as disclosed in thelatter patent r may be left uncovered as disclosed in the earlierpatent. I

Throughout the specifications and claims I carbon and carbonaceousvmaterial is used in the broader sense and includes the graphitic stateof the element.

This application is a division of m cogending application, Serial No.42,092, filed uly 7, 1925.

I claim:

1. The method of making a pure de olarizer which comprises the steps ofoxi izing carbonaceous material and then chemically precipitatingmanganese dioxide onto suspended particles of said oxidized material,substantially as described.

2. The method of making a pure de olarizer which comprises the steps ofoxi izing carbonaceous material, suspending the oxidized material in anacidified manganese solution, and slowly precipitating manganese dioxideon the suspended material, substantially as described.

3. The method of making a pure depolarizer which comprises the steps ofoxidizing carbonaceous material, suspending theoxidized material in asolution ofpotassium permanganate and manganese sulphate andprecipitating man anese dioxide on said suspended material y means ofnitric acid, substantially as described.

In testimony whereof I aflix my signature.

BRUCE K. BROWN.

